Programming Forums > Application Development > C++

357mag · Jul 26th, 2007, 4:03 AM

I'm trying to understand the classic compute the factorial of a number business using recursion. Let's say I want to compute the factorial of 4 so in my main function I have something like this:

(Toggle Plain Text)

int x = 4;

cout << factorial(x);

Then my function definition goes like this:

(Toggle Plain Text)

int factorial(int number)
{
   if (number <= 1)
      return 1;

   else
      return number * factorial(number - 1);
}

I guess the way I got it figured so far is this. The value of x which is 4 gets passed to number. Then we have a succession of function calls like this:

(Toggle Plain Text)

return 4 * factorial(3)
return 3 * factorial(2)
return 3 * factorial(1)

And I think then that would be all. But it's hard to see the intermediate results with all these successive function calls. One of my books does recommend putting in a statement that would print the level at which each call is and what the intermediate result is. In order for me to do that, would I just do this?

(Toggle Plain Text)

else
   cout << n * factorial(n - 1)

Let me know what the best way to understand this is.

Jul 26th, 2007, 4:03 AM	#1
357mag Hobbyist Programmer Join Date: Mar 2005 Posts: 148 Rep Power: 4	Understanding Recursion I'm trying to understand the classic compute the factorial of a number business using recursion. Let's say I want to compute the factorial of 4 so in my main function I have something like this: (Toggle Plain Text) int x = 4; cout << factorial(x); int x = 4; cout << factorial(x); Then my function definition goes like this: (Toggle Plain Text) int factorial(int number) { if (number <= 1) return 1; else return number * factorial(number - 1); } int factorial(int number) { if (number <= 1) return 1; else return number * factorial(number - 1); } I guess the way I got it figured so far is this. The value of x which is 4 gets passed to number. Then we have a succession of function calls like this: (Toggle Plain Text) return 4 * factorial(3) return 3 * factorial(2) return 3 * factorial(1) return 4 * factorial(3) return 3 * factorial(2) return 3 * factorial(1) And I think then that would be all. But it's hard to see the intermediate results with all these successive function calls. One of my books does recommend putting in a statement that would print the level at which each call is and what the intermediate result is. In order for me to do that, would I just do this? (Toggle Plain Text) else cout << n * factorial(n - 1) else cout << n * factorial(n - 1) Let me know what the best way to understand this is.

Programming Forums > Application Development > C++

Understanding Recursion